This invention relates to a photothermographic material capable of forming an image faithful to exposure and more particularly, to a photographic photothermographic material suitable for printing plate application.
As scanners and image setters capable of exposure with lasers and light-emitting diodes become widespread as output devices in the graphic printing field, there is a demand for graphic printing photosensitive material having high sensitivity, Dmax, contrast and image quality. From the contemporary standpoints of environmental protection and space saving, it is strongly desired to reduce the quantity of spent solution associated with conventional wet system photographic silver halide photosensitive material. One approach for reducing the spent solution to zero is the utilization of thermographic photographic recording material.
In order that photographic photothermographic material produce an image faithful to exposure and having high resolution, it is effective to add an anti-irradiation dye or provide an anti-halation layer like the conventional wet system photographic silver halide photosensitive material. The anti-irradiation dye is mainly added to the photosensitive layer while the anti-halation layer is disposed between the support and the photosensitive layer or on that side of the support remote from the photosensitive layer. For example, where an output of a near infrared laser is to be recorded, a dye having absorption in the infrared region is necessary. Exemplary infrared dyes include indolenine cyanine dyes as described in JP-A 182640/1992 and dihydroperimidine squarylium dyes having squaric acid bonded to a dihydroperimidine nucleus at its para-position as described in U.S. Pat. No. 5,380,635.
One method for producing photographic photothermographic material having high Dmax and contrast is to add hydrazine derivatives to photosensitive material as described in U.S. Pat. No. 5,496,695. Although a photographic photothermographic material having high Dmax and ultrahigh contrast is obtained, it still has the drawback that upon exposure by means of a laser image setter, images in exposed areas thicken and large spots collapse. Since the recent further advance of laser image setters enables high precision exposure, there is a strong need for a photosensitive material capable of forming images faithful to exposure in a reproducible manner.
U.S. Pat. No. 5,545,515 describes a photographic photothermographic material comprising a hydrazine derivative of specific structure. It is also disclosed that an indolenine cyanine dye is added to an anti-halation or back layer. However, there is not available a dye which can prevent irradiation within the photosensitive layer or prevent halation between the photosensitive layer and the support. To produce an ultrahigh contrast image faithful to exposure, an anti-irradiation or anti-halation dye having no influence on image formation within the photosensitive layer is needed.